Systems for tissue resection, ablation and aspiration

ABSTRACT

The present invention provides systems and methods for selectively applying electrical energy to a target location within or on a patient&#39;s body. In particular, methods and apparatus are provided for resecting, cutting, partially ablating, aspirating or otherwise removing tissue from a target site, and ablating the tissue in situ. The systems and methods of the present invention are particularly useful for ablation and hemostasis of tissue in sinus surgery (e.g., chronic sinusitis and/or removal of polypectomies) and for resecting and ablating soft tissue structures, such as the meniscus and synovial tissue within a joint.

RELATED APPLICATIONS

The present invention is division of U.S. application Ser. No.09/010,382, filed on Jan. 21, 1998 now U.S. Pat. No. 6,190,381 which isa continuation-in-part of U.S. patent application entitled “Systems andMethods for Electrosurgical Sinus Surgery”, Ser. No. 08/990,374 filed onDec. 15, 1997 now U.S. Pat. No. 6,109,268, which is acontinuation-in-part of application Ser. No. 08/485,219, filed on Jun.7, 1995, now U.S. Pat. No. 5,697,281, the complete disclosure of whichis incorporated herein by reference for all purposes. The presentinvention also derives priority from Provisional patent applicationentitled “Systems and Methods for Electrosurgical Tissue Resection andAblation”, filed on Oct. 23, 1997.

The present invention is related to commonly assigned co-pendingProvisional patent application entitled “Systems and Methods forElectrosurgical Tissue and Fluid Coagulation”, filed on Oct. 23, 1997,non-provisional U.S. patent applications entitled “Systems and Methodsfor Electrosurgical Dermatological Treatment”, filed on Nov. 25, 1997,entitled ‘SYSTEMS AND METHODS FOR ELECTROSURGICAL TISSUE CONTRACTION”,filed on Oct. 2, 1997, U.S. application Ser. No. 08/753,227, filed onNov. 22, 1996, U.S. application Ser. No. 08/687,792, filed on Jul. 18,1996, and PCT International Application, U.S. National Phase Ser. No.PCT/US94/05168, filed on May 10, 1994, which was a continuation-in-partof application Ser. No. 08/059,681, filed on May 10, 1993, which was acontinuation-in-part of application Ser. No. 07/958,977, filed on Oct.9, 1992 which was a continuation-in-part of application Ser. No.07/817,575, filed on Jan. 7, 1992, the complete disclosures of which areincorporated herein by reference for all purposes. The present inventionis also related to commonly assigned U.S. Pat. No. 5,683,366, filed Nov.22, 1995, the complete disclosure of which is incorporated herein byreference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of electrosurgery,and more particularly to surgical devices and methods which employ highfrequency electrical energy to resect, coagulate, ablate and aspiratecartilage, bone and tissue, such as sinus tissue, or meniscus andsynovial tissue in a joint.

Conventional electrosurgical methods are widely used since theygenerally reduce patient bleeding associated with tissue cuttingoperations and improve the surgeon's visibility. These electrosurgicaldevices and procedures, however, suffer from a number of disadvantages.For example, monopolar electrosurgery methods generally direct electriccurrent along a defined path from the exposed or active electrodethrough the patient's body to the return electrode, which is externallyattached to a suitable location on the patient's skin. In addition,since the defined path through the patient's body has a relatively highelectrical impedance, large voltage differences must typically beapplied between the active and return electrodes to generate a currentsuitable for cutting or coagulation of the target tissue. This current,however, may inadvertently flow along localized pathways in the bodyhaving less impedance than the defined electrical path. This situationwill substantially increase the current flowing through these paths,possibly causing damage to or destroying tissue along and surroundingthis pathway.

Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient beyond the immediate site of application of the bipolarelectrodes. In bipolar devices, both the active and return electrode aretypically exposed so that they may both contact tissue, therebyproviding a return current path from the active to the return electrodethrough the tissue. One drawback with this configuration, however, isthat the return electrode may cause tissue desiccation or destruction atits contact point with the patient's tissue.

Another limitation of conventional bipolar and monopolar electrosurgerydevices is that they are not suitable for the precise removal (i.e.,ablation) or tissue. In addition, conventional electrosurgical methodsare generally not that effective with certain types of tissue, and incertain types of environments within the body. For example, loose orelastic connective tissue, such as the synovial tissue in joints, isextremely difficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to or in contact with the elastic tissue for a long enoughperiod of time to energize the electrode and conduct current through thetissue.

The use of electrosurgical procedures (both monopolar and bipolar) inelectrically conductive environments can be further problematic. Forexample, many arthroscopic procedures require flushing of the region tobe treated with isotonic saline, both to maintain an isotonicenvironment and to keep the field of view clear. However, the presenceof saline, which is a highly conductive electrolyte, can cause shortingof the active electrode(s) in conventional monopolar and bipolarelectrosurgery. Such shorting causes unnecessary heating in thetreatment environment and can further cause non-specific tissuedestruction.

Conventional electrosurgical cutting or resecting devices also tend toleave the operating field cluttered with tissue fragments that have beenremoved or resected from the target tissue. These tissue fragments makevisualization of the surgical site extremely difficult. Removing thesetissue fragments can also be problematic. Similar to synovial tissue, itis difficult to maintain contact with tissue fragments long enough toablate the tissue fragments in situ with conventional devices. To solvethis problem, the surgical site is periodically or continuouslyaspirated during the procedure. However, the tissue fragments often clogthe aspiration lumen of the suction instrument, forcing the surgeon toremove the instrument to clear the aspiration lumen or to introduceanother suction instrument, which increases the length and complexity ofthe procedure.

SUMMARY OF THE INVENTION

The present invention provides systems, apparatus and methods forselectively applying electrical energy to structures within or on thesurface of a patient's body. In particular, methods and apparatus areprovided for resecting, cutting, partially ablating, aspirating orotherwise removing tissue from a target site, and ablating the tissue insitu. The systems and methods of the present invention are particularlyuseful for ablation and hemostasis of tissue in sinus surgery (e.g.,chronic sinusitis and/or removal of polypectomies) and for resecting andablating soft tissue structures, such as the meniscus and synovialtissue within a joint.

In one aspect of the invention, a method comprises introducing a distalend of an electrosurgical instrument, such as a probe or a catheter, tothe target site, and aspirating tissue from the target site through oneor more aspiration lumen(s) in the instrument. High frequency voltage isapplied between one or more aspiration electrode(s) coupled to theaspiration lumen(s) and one or more return electrode(s) so that anelectric current flows therebetween. The high frequency voltage issufficient to remove or ablate at least a portion of the tissue beforethe tissue passes into the aspiration lumen(s). This partial or totalablation reduces the size of the aspirated tissue fragments to inhibitclogging of the aspiration lumen.

The aspiration electrode(s) are usually located near or at the distalopening of the aspiration lumen so that tissue can be partially ablatedbefore it becomes clogged in the aspiration lumen. In some embodiments,the aspiration electrodes(s) are adjacent to the distal opening, or theymay extend across the distal opening of the lumen. The latterconfiguration has the advantage of ensuring that the tissue passingthrough the aspiration lumen will contact the aspiration electrode(s).In other embodiments, the aspiration electrode(s) may be positionedwithin the aspiration lumen just proximal of the distal opening. Theaspiration electrode(s) may comprise a loop, a coiled structure, a hook,or any other geometry suitable for ablating the aspirated tissue. In anexemplary embodiment, the electrosurgical probe comprises a pair of loopelectrodes disposed across the distal end of the suction lumen.

The electrosurgical probe will preferably also include one or moreablation electrode(s) for removing or ablating tissue at the targetsite. Typically, the ablation electrode(s) are different from theaspiration electrode(s), although the same electrodes may serve bothfunctions. In an exemplary embodiment, the probe includes a plurality ofelectrically isolated electrode terminals surrounding the distal openingof the aspiration lumen. High frequency voltage is applied between theelectrode terminals and a return electrode to ablate tissue at thetarget site. During the procedure, fluid and/or non-ablated tissuefragments are aspirated from the target site to improve visualization.Preferably, one or more of the electrode terminals are loop electrodesthat extend across the distal opening of the suction lumen to ablate, orat least reduce the volume of, the tissue fragments, thereby inhibitingclogging of the lumen. The aspiration or lop electrodes may be energizedwith the active electrode terminal(s), or they may be isolated from theelectrode terminal(s) so that the surgeon may select which electrodesare activated during the procedure.

In some embodiments, the return electrode(s) comprises an annularelectrode member on the probe itself, spaced proximally from theaspiration and ablation electrodes. In these embodiments, electricallyconducting fluid, such as isotonic saline, is preferably used togenerate a current flow path between the aspiration electrode(s) and thereturn electrode(s). High frequency voltage is then applied between theelectrode terminal(s) and the return electrode(s) through the currentflow path created by the electrically conducting fluid. Depending on theprocedure, the electrically conductive fluid may be delivered to thetarget site through, for example, a fluid lumen in the probe or aseparate instrument, or the fluid may already be present at the targetsite, as is the case in many arthroscopic procedures.

In a specific configuration, the tissue is removed by moleculardissociation or disintegration processes. In these embodiments, the highfrequency voltage applied to the electrode terminal(s) is sufficient tovaporize an electrically conductive fluid (e.g., gel or saline) betweenthe electrode terminal(s) and the tissue. Within the vaporized fluid, aionized plasma is formed and charged particles (e.g., electrons) areaccelerated towards the tissue to cause the molecular breakdown ordisintegration of several cell layers of the tissue. This moleculardissociation is accompanied by the volumetric removal of the tissue. Theshort range of the accelerated charged particles within the plasma layerconfines the molecular dissociation process to the surface layer tominimize damage and necrosis to the underlying tissue. This process canbe precisely controlled to effect the volumetric removal of tissue asthin as 10 to 150 microns with minimal heating of, or damage to,surrounding or underlying tissue structures. A more complete descriptionof this phenomena is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

The present invention offers a number of advantages over conventionalelectrosurgery, microdebrider and laser techniques for removing softtissue in arthroscopic, sinus or other surgical procedures. The abilityto precisely control the volumetric removal of tissue results in a fieldof tissue ablation or removal that is very defined, consistent andpredictable. The shallow depth of tissue heating also helps to minimizeor completely eliminate damage to healthy tissue structures, cartilage,bone and/or cranial nerves that are often adjacent the target sinustissue. In addition, small blood vessels at the target site aresimultaneously cauterized and sealed as the tissue is removed tocontinuously maintain hemostasis during the procedure. This increasesthe surgeon's field of view, and shortens the length of the procedure.Moreover, since the present invention allows for the use of electricallyconductive fluid (contrary to prior art bipolar and monopolarelectrosurgery techniques), isotonic saline may be used during theprocedure. Saline is the preferred medium for irrigation because it hasthe same concentration as the body's fluids and, therefore, is notabsorbed into the body as much as other fluids.

In another aspect of the invention, a method comprises positioning oneor more resection electrode(s) adjacent the target tissue, and applyinghigh frequency voltage between the resection electrode(s) and one ormore return electrode(s) to resect a tissue fragment away from thetissue structure. High frequency voltage is then applied between one ormore ablation electrode(s) and one or more return electrode(s) to ablatethe tissue fragment in situ. The ablation electrode(s) may be the sameelectrodes as the resection electrode(s), or they may be differentelectrodes spaced from the resection electrode(s). Removing the resectedtissue fragments improves the surgeon's visibility of the target site,and eliminates the potential of this tissue from remaining in the bodyafter the surgical procedure.

Alternatively, the loop electrode(s) may be used to ablate (i.e.,volumetrically remove) tissue directly at the target site using themechanisms described above. Applicant has found that the loopelectrode(s) have a larger surface area exposed to electricallyconductive fluid than the active electrode terminals described above.Therefore, the loop electrode(s) typically provide a stronger plasmalayer, which leads to faster tissue ablation rates for the same appliedvoltage levels. In addition, the loop electrode configuration provides arelative smooth, uniform cutting effect across the tissue.

In a specific configuration, an electrosurgical probe according to theinvention comprises a shaft having an electrically insulating support ator near the distal end of the shaft. The instrument further includes oneor more loop electrode(s) extending from the insulating support forresection or ablation of tissue, and one or more electrode terminal(s)for ablation of tissue fragments that have been resected by the loopelectrode(s.) The electrode terminal(s) may comprise an array ofelectrode terminals or a single electrode at the distal end of theelectrosurgical probe. In a specific embodiment, one or more returnelectrode(s) are positioned in contact with electrically conductingfluid to provide a current flow path from the electrode terminal(s),through the electrically conducting fluid, to the return electrode(s).

In yet another aspect of the invention, a method comprises positioningone or more active electrode(s) at the target site within a patient'sbody and applying a suction force to a tissue structure to draw thetissue structure to the active electrode(s). High frequency voltage isthen applied between the active electrode(s) and one or more returnelectrode(s) to ablate the tissue structure. Typically, the tissuestructure comprises a flexible or elastic connective tissue, such assynovial tissue. This type of tissue is typically difficult to removewith conventional mechanical and electrosurgery techniques because thetissue moves away from the instrument. The present invention, bycontrast, draws the elastic tissue towards the active electrodes, andthen ablates this tissue with the mechanisms described above

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrosurgical system incorporatinga power supply and an electrosurgical probe for tissue ablation,resection, incision, contraction and for vessel hemostasis according tothe present invention;

FIG. 2 is a side view of an electrosurgical probe according to thepresent invention incorporating a loop electrode for resection andablation of tissue;

FIG. 3 is a cross sectional view of the electrosurgical probe of FIG. 1;

FIG. 4 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIGS. 5A and 5B are end and cross-sectional views, respectively, of theproximal portion of the probe;

FIG. 6 illustrates a surgical kit for removing and ablating tissueaccording to the present invention;

FIG. 7 is a perspective view of another electrosurgical systemincorporating a power supply, an electrosurgical probe and a supply ofelectrically conductive fluid for delivering the fluid to the targetsite;

FIG. 8 is a side view of another electrosurgical probe according to thepresent invention incorporating aspiration electrodes for ablatingaspirated tissue fragments and/or tissue strands, such as synovialtissue;

FIG. 9 is an end view of the probe of FIG. 8;

FIG. 10 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIGS. 11-13 illustrate alternative probes according to the presentinvention, incorporating aspiration electrodes;

FIG. 14 illustrates an endoscopic sinus surgery procedure, wherein anendoscope is delivered through a nasal passage to view a surgical sitewithin the nasal cavity of the patient;

FIG. 15 illustrates an endoscopic sinus surgery procedure with one ofthe probes described above according to the present invention;

FIGS. 16A and 16B illustrate a detailed view of the sinus surgeryprocedure, illustrating ablation of tissue according to the presentinvention; and

FIG. 17 illustrates a procedure for treating obstructive sleepdisorders, such as sleep apnea, according to the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides systems and methods for selectivelyapplying electrical energy to a target location within or on a patient'sbody. The present invention is particularly useful in procedures wherethe tissue site is flooded or submerged with an electrically conductingfluid, such as arthroscopic surgery of the knee, shoulder, ankle, hip,elbow, hand or foot. In addition, tissues which may be treated by thesystem and method of the present invention include, but are not limitedto, prostate tissue and leiomyomas (fibroids) located within the uterus,gingival tissues and mucosal tissues located in the mouth, tumors, scartissue, myocardial tissue, collagenous tissue within the eye orepidermal and dermal tissues on the surface of the skin. Otherprocedures include laminectomy/disketomy procedures for treatingherniated disks, decompressive laminectomy for stenosis in thelumbosacral and cervical spine, posterior lumbosacral and cervical spinefusions, treatment of scoliosis associated with vertebral disease,foraminotomies to remove the roof of the intervertebral foramina torelieve nerve root compression and anterior cervical and lumbardiskectomies. The present invention is also useful for resecting tissuewithin accessible sites of the body that are suitable for electrode loopresection, such as the resection of prostate tissue, leiomyomas(fibroids) located within the uterus and other diseased tissue withinthe body.

The present invention is also useful for procedures in the head andneck, such as the ear, mouth, pharynx, larynx, esophagus, nasal cavityand sinuses. These procedures may be performed through the mouth or noseusing speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, and salivaryglands, submucus resection of the nasal septum, excision of diseasedtissue and the like. In other procedures, the present invention may beuseful for collagen shrinkage, ablation and/or hemostasis in proceduresfor treating snoring and obstructive sleep apnea (e.g., soft palate,such as the uvula, or tongue/pharynx stiffening, and midlineglossectomies), for gross tissue removal, such as tonsillectomies,adenoidectomies, tracheal stenosis and vocal cord polyps and lesions, orfor the resection or ablation of facial tumors or tumors within themouth and pharynx, such as glossectomies, laryngectomies, acousticneuroma procedures and nasal ablation procedures. In addition, thepresent invention is useful for procedures within the ear, such asstapedotomies, tympanostomies or the like.

The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention is particularly useful for ablation and sculpting of cartilagetissue, such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck, e.g., the removal of pigmentations,vascular lesions (e.g., leg veins), scars, tattoos, etc., and for othersurgical procedures on the skin, such as tissue rejuvenation, cosmeticeye procedures (blepharoplasties), wrinkle removal, tightening musclesfor facelifts or browlifts, hair removal and/or transplant procedures,etc.

For convenience, the remaining disclosure will be directed specificallyto the resection and/or ablation of the meniscus and the synovial tissuewithin a joint during an arthroscopic procedure and to the ablation,resection and/or aspiration of sinus tissue during an endoscopic sinussurgery procedure, but it will be appreciated that the system and methodcan be applied equally well to procedures involving other tissues of thebody, as well as to other procedures including open procedures,intravascular procedures, urology, laparoscopy, arthroscopy,thoracoscopy or other cardiac procedures, dermatology, orthopedics,gynecology, otorhinolaryngology, spinal and neurologic procedures,oncology and the like.

In the present invention, high frequency (RF) electrical energy isapplied to one or more electrode terminals in the presence ofelectrically conductive fluid to remove and/or modify the structure oftissue structures. Depending on the specific procedure, the presentinvention may be used to: (1) volumetrically remove tissue, bone orcartilage (i.e., ablate or effect molecular dissociation of the tissuestructure); (2) cut or resect tissue; (3) shrink or contract collagenconnective tissue; and/or (4) coagulate severed blood vessels.

In one aspect of the invention, systems and methods are provided for thevolumetric removal or ablation of tissue structures. In theseprocedures, a high frequency voltage difference is applied between oneor more electrode terminal(s) and one or more return electrode(s) todevelop high electric field intensities in the vicinity of the targettissue site. The high electric field intensities lead to electric fieldinduced molecular breakdown of target tissue through moleculardissociation (rather than thermal evaporation or carbonization).Applicant believes that the tissue structure is volumetrically removedthrough molecular disintegration of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxides of carbon,hydrocarbons and nitrogen compounds. This molecular disintegrationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of liquid within the cells of the tissue,as is typically the case with electrosurgical desiccation andvaporization.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconducting fluid over at least a portion of the electrode terminal(s) inthe region between the distal tip of the electrode terminal(s) and thetarget tissue. The electrically conductive fluid may be a gas or liquid,such as isotonic saline, delivered to the target site, or a viscousfluid, such as a gel, that is located at the target site. In the latterembodiment, the electrode terminal(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itincreases the voltage differential between the electrode terminal tipand the tissue and causes ionization within the vapor layer due to thepresence of an ionizable species (e.g., sodium when isotonic saline isthe electrically conducting fluid). This ionization, under optimalconditions, induces the discharge of energetic electrons and photonsfrom the vapor layer and to the surface of the target tissue. Thisenergy may be in the form of energetic photons (e.g., ultravioletradiation), energetic particles (e.g., electrons) or a combinationthereof. A more detailed description of this cold ablation phenomena,termed Coblation™, can be found in commonly assigned U.S. Pat. No.5,683,366 the complete disclosure of which is incorporated herein byreference.

The present invention applies high frequency (RF) electrical energy inan electrically conducting fluid environment to remove (i.e., resect,cut or ablate) or contract a tissue structure, and to seal transectedvessels within the region of the target tissue. The present invention isparticularly useful for sealing larger arterial vessels, e.g., on theorder of 1 mm or greater. In some embodiments, a high frequency powersupply is provided having an ablation mode, wherein a first voltage isapplied to an electrode terminal sufficient to effect moleculardissociation or disintegration of the tissue, and a coagulation mode,wherein a second, lower voltage is applied to an electrode terminal(either the same or a different electrode) sufficient to achievehemostasis of severed vessels within the tissue. In other embodiments,an electrosurgical probe is provided having one or more coagulationelectrode(s) configured for sealing a severed vessel, such as anarterial vessel, and one or more electrode terminals configured foreither contracting the collagen fibers within the tissue or removing(ablating) the tissue, e.g., by applying sufficient energy to the tissueto effect molecular dissociation. In the latter embodiments, thecoagulation electrode(s) may be configured such that a single voltagecan be applied to coagulate with the coagulation electrode(s), and toablate or contract with the electrode terminal(s). In other embodiments,the power supply is combined with the coagulation probe such that thecoagulation electrode is used when the power supply is in thecoagulation mode (low voltage), and the electrode terminal(s) are usedwhen the power supply is in the ablation mode (higher voltage).

In the method of the present invention, one or more electrode terminalsare brought into close proximity to tissue at a target site, and thepower supply is activated in the ablation mode such that sufficientvoltage is applied between the electrode terminals and the returnelectrode to volumetrically remove the tissue through moleculardissociation, as described below. During this process, vessels withinthe tissue will be severed. Smaller vessels will be automatically sealedwith the system and method of the present invention. Larger vessels, andthose with a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by activating a control (e.g., a foot pedal) toreduce the voltage of the power supply into the coagulation mode. Inthis mode, the electrode terminals may be pressed against the severedvessel to provide sealing and/or coagulation of the vessel.Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon activates a control (e.g.,another foot pedal) to increase the voltage of the power supply backinto the ablation mode.

The present invention is particularly useful for removing or ablatingtissue around nerves, such as spinal or cranial nerves, e.g., theolfactory nerve on either side of the nasal cavity, the optic nervewithin the optic and cranial canals, the palatine nerve within the nasalcavity, soft palate, uvula and tonsil, etc. One of the significantdrawbacks with the prior art microdebriders and lasers is that thesedevices do not differentiate between the target tissue and thesurrounding nerves or bone. Therefore, the surgeon must be extremelycareful during these procedures to avoid damage to the bone or nerveswithin and around the nasal cavity. In the present invention, theCoblation™ process for removing tissue results in extremely small depthsof collateral tissue damage as discussed above. This allows the surgeonto remove tissue close to a nerve without causing collateral damage tothe nerve fibers.

In addition to the generally precise nature of the novel mechanisms ofthe present invention, applicant has discovered an additional method ofensuring that adjacent nerves are not damaged during tissue removal.According to the present invention, systems and methods are provided fordistinguishing between the fatty tissue immediately surrounding nervefibers and the normal tissue that is to be removed during the procedure.Nerves usually comprise a connective tissue sheath, or endoneurium,enclosing the bundles of nerve fibers to protect these nerve fibers.This protective tissue sheath typically comprises a fatty tissue (e.g.,adipose tissue) having substantially different electrical propertiesthan the normal target tissue, such as the turbinates, polyps, mucustissue or the like, that are, for example, removed from the nose duringsinus procedures. The system of the present invention measures theelectrical properties of the tissue at the tip of the probe with one ormore electrode terminal(s). These electrical properties may includeelectrical conductivity at one, several or a range of frequencies (e.g.,in the range from 1 kHz to 100 MHz), dielectric constant, capacitance orcombinations of these. In this embodiment, an audible signal may beproduced when the sensing electrode(s) at the tip of the probe detectsthe fatty tissue surrounding a nerve, or direct feedback control can beprovided to only supply power to the electrode terminal(s) eitherindividually or to the complete array of electrodes, if and when thetissue encountered at the tip or working end of the probe is normaltissue based on the measured electrical properties.

In one embodiment, the current limiting elements (discussed in detailabove) are configured such that the electrode terminals will shut downor turn off when the electrical impedance reaches a threshold level.When this threshold level is set to the impedance of the fatty tissuesurrounding nerves, the electrode terminals will shut off whenever theycome in contact with, or in close proximity to, nerves. Meanwhile, theother electrode terminals, which are in contact with or in closeproximity to nasal tissue, will continue to conduct electric current tothe return electrode. This selective ablation or removal of lowerimpedance tissue in combination with the Coblation™ mechanism of thepresent invention allows the surgeon to precisely remove tissue aroundnerves or bone.

In addition to the above, applicant has discovered that the Coblation™mechanism of the present invention can be manipulated to ablate orremove certain tissue structures, while having little effect on othertissue structures. As discussed above, the present invention uses atechnique of vaporizing electrically conductive fluid to form a plasmalayer or pocket around the electrode terminal(s), and then inducing thedischarge of energy from this plasma or vapor layer to break themolecular bonds of the tissue structure. Based on initial experiments,applicants believe that the free electrons within the ionized vaporlayer are accelerated in the high electric fields near the electrodetip(s). When the density of the vapor layer (or within a bubble formedin the electrically conducting liquid) becomes sufficiently low (i.e.,less than approximately 10²⁰ atoms/cm³ for aqueous solutions), theelectron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within these regions of low density(i.e., vapor layers or bubbles). Energy evolved by the energeticelectrons (e.g., 4 to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine into final gaseous or liquid species.

The energy evolved by the energetic electrons may be varied by adjustinga variety of factors, such as: the number of electrode terminals;electrode size and spacing; electrode surface area; asperities and sharpedges on the electrode surfaces; electrode materials; applied voltageand power; current limiting means, such as inductors; electricalconductivity of the fluid in contact with the electrodes; density of thefluid; and other factors. Accordingly, these factors can be manipulatedto control the energy level of the excited electrons. Since differenttissue structures have different molecular bonds, the present inventioncan be configured to break the molecular bonds of certain tissue, whilehaving too low an energy to break the molecular bonds of other tissue.For example, fatty tissue, (e.g., adipose) tissue has double bonds thatrequire a substantially higher energy level than 4 to 5 eV to break.Accordingly, the present invention in its current configurationgenerally does not ablate or remove such fatty tissue. Of course,factors may be changed such that these double bonds can be broken (e.g.,increasing voltage or changing the electrode configuration to increasethe current density at the electrode tips).

In another aspect of the invention, a loop electrode is employed toresect, shape or otherwise remove tissue fragments from the treatmentsite, and one or more electrode terminals are employed to ablate (i.e.,break down the tissue by processes including molecular dissociation ordisintegration) the non-ablated tissue fragments in situ. Once a tissuefragment is cut, partially ablated or resected by the loop electrode,one or more electrode terminals will be brought into close proximity tothese fragments (either by moving the probe into position, or by drawingthe fragments to the electrode terminals with a suction lumen). Voltageis applied between the electrode terminals and the return electrode tovolumetrically remove the fragments through molecular dissociation, asdescribed above. The loop electrode and the electrode terminals arepreferably electrically isolated such that, for example, current can belimited (passively or actively) or completely interrupted to the loopelectrode as the surgeon employs the electrode terminals to ablatetissue fragments (and vice versa).

In another aspect of the invention, the loop electrode(s) are employedonly to ablate tissue using the Coblation™ mechanisms described above.In these embodiments, the loop electrode(s) provides a relativelyuniform smooth cutting or ablation effect across the tissue. Inaddition, loop electrodes generally have a larger surface area exposedto electrically conductive fluid (as compared to the smaller electrodeterminals described above), which increases the rate of ablation oftissue. Preferably, the loop electrode(s) extend a sufficient distancefrom the electrode support member selected to achieve a desirableablation rate, while minimizing power dissipation into the surroundingmedium (which could cause undesirable thermal damage to surrounding orunderlying tissue). In an exemplary embodiment, the loop electrode has alength from one end to the other end of about 0.5 to 20 mm, usuallyabout 1 to 8 mm. The loop electrode usually extends about 0.25 to 10 mmfrom the distal end of the support member, preferably about 1 to 4 mm.

The loop electrode(s) may have a variety of cross-sectional shapes.Electrode shapes according to the present invention can include the useof formed wire (e.g., by drawing round wire through a shaping die) toform electrodes with a variety of cross-sectional shapes, such assquare, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

In some embodiments, the loop electrode(s) will have a “non-active”portion or surface to selectively reduce undesirable current flow fromthe non-active portion or surface into tissue or surroundingelectrically conducting liquids (e.g., isotonic saline, blood orblood/non-conducting irrigant mixtures). Preferably, the “non-active”electrode portion will be coated with an electrically insulatingmaterial. This can be accomplished, for example, with plasma depositedcoatings of an insulating material, thin-film deposition of aninsulating material using evaporative or sputtering techniques (e.g.,SiO2 or Si3N4), dip coating, or by providing an electrically insulatingsupport member to electrically insulate a portion of the externalsurface of the electrode. The electrically insulated non-active portionof the active electrode(s) allows the surgeon to selectively resectand/or ablate tissue, while minimizing necrosis or ablation ofsurrounding non-target tissue or other body structures.

In addition, the loop electrode(s) may comprise a single electrodeextending from first and second ends to an insulating support in theshaft, or multiple, electrically isolated electrodes extending aroundthe loop. One or more return electrodes may also be positioned along theloop portion. Further descriptions of these configurations can be foundin U.S. application Ser. No. 08/687,792, filed on Jul. 18, 1996, whichas already been incorporated herein by reference.

The electrosurgical probe will comprise a shaft or a handpiece having aproximal end and a distal end which supports one or more electrodeterminal(s). The shaft or handpiece may assume a wide variety ofconfigurations, with the primary purpose being to mechanically supportthe active electrode and permit the treating physician to manipulate theelectrode from a proximal end of the shaft. The shaft may be rigid orflexible, with flexible shafts optionally being combined with agenerally rigid external tube for mechanical support. The distal portionof the shaft may comprise a flexible material, such as plastics,malleable stainless steel, etc, so that the physician can mold thedistal portion into different configurations for different applications.Flexible shafts may be combined with pull wires, shape memory actuators,and other known mechanisms for effecting selective deflection of thedistal end of the shaft to facilitate positioning of the electrodearray. The shaft will usually include a plurality of wires or otherconductive elements running axially therethrough to permit connection ofthe electrode array to a connector at the proximal end of the shaft.Thus, the shaft will typically have a length of at least 5 cm for oralprocedures and at least 10 cm, more typically being 20 cm, or longer forendoscopic procedures. The shaft will typically have a diameter of atleast 0.5 mm and frequently in the range from 1 to 10 mm. Of course, fordermatological procedures on the outer skin, the shaft may have anysuitable length and diameter that would facilitate handling by thesurgeon.

For procedures within the nose, the shaft will have a suitable diameterand length to allow the surgeon to reach the target site (e.g., ablockage in the nasal cavity or one of the sinuses) by delivering theprobe shaft through one of the nasal passages or another opening (e.g.,an opening in the eye or through an opening surgically creating duringthe procedure). Thus, the shaft will usually have a length in the rangeof about 5-25 cm, and a diameter in the range of about 0.5 to 5 mm. Forprocedures requiring the formation of a small hole or channel in tissue,such as treating swollen turbinates, the shaft diameter will usually beless than 3 mm, preferably less than about 1 mm. Likewise, forprocedures in the ear, the shaft should have a length in the range ofabout 3 to 20 cm, and a diameter of about 0.3 to 5 mm. For procedures inthe mouth or upper throat, the shaft will have any suitable length anddiameter that would facilitate handling by the surgeon. For proceduresin the lower throat, such as laryngectomies, the shaft will be suitablydesigned to access the larynx. For example, the shaft may be flexible,or have a distal bend to accommodate the bend in the patient's throat.In this regard, the shaft may be a rigid shaft having a specificallydesigned bend to correspond with the geometry of the mouth and throat,or it may have a flexible distal end, or it may be part of a catheter.In any of these embodiments, the shaft may also be introduced throughrigid or flexible endoscopes. Specific shaft designs will be describedin detail in connection with the figures hereinafter.

The current flow path between the electrode terminal(s) and the returnelectrode(s) may be generated by submerging the tissue site in anelectrical conducting fluid (e.g., within a viscous fluid, such as anelectrically conductive gel) or by directing an electrically conductingfluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry environment (i.e., the tissue is notsubmerged in fluid) because the electrically conducting fluid provides asuitable current flow path from the electrode terminal to the returnelectrode. A more complete description of an exemplary method ofdirecting electrically conducting fluid between the active and returnelectrodes is described in parent application Ser. No. 08/485,219, filedJun. 7, 1995, previously incorporated herein by reference.

In some procedures, it may also be necessary to retrieve or aspirate theelectrically conductive fluid after it has been directed to the targetsite. For example, in procedures in the nose, mouth or throat, it may bedesirable to aspirate the fluid so that it does not flow down thepatient's throat. In addition, it may be desirable to aspirate smallpieces of tissue that are not completely disintegrated by the highfrequency energy, or other fluids at the target site, such as blood,mucus, the gaseous products of ablation, etc. Accordingly, the system ofthe present invention will usually include a suction lumen in the probe,or on another instrument, for aspirating fluids from the target site.

In some embodiments, the probe will include one or more aspirationelectrode(s) coupled to the distal end of the suction lumen forablating, or at least reducing the volume of, non-ablated tissuefragments that are aspirated into the lumen. The aspiration electrode(s)function mainly to inhibit clogging of the lumen that may otherwiseoccur as larger tissue fragments are drawn therein. The aspirationelectrode(s) may be different from the ablation electrode terminal(s),or the same electrode(s) may serve both functions. In some embodiments,the probe will be designed to use suction force to draw loose tissue,such as synovial tissue to the aspiration or ablation electrode(s) onthe probe, which are then energized to ablate the loose tissue.

The present invention may use a single active electrode terminal or anelectrode array distributed over a contact surface of a probe. In thelatter embodiment, the electrode array usually includes a plurality ofindependently current-limited and/or power-controlled electrodeterminals to apply electrical energy selectively to the target tissuewhile limiting the unwanted application of electrical energy to thesurrounding tissue and environment resulting from power dissipation intosurrounding electrically conductive liquids, such as blood, normalsaline, electrically conductive gel and the like. The electrodeterminals may be independently current-limited by isolating theterminals from each other and connecting each terminal to a separatepower source that is isolated from the other electrode terminals.Alternatively, the electrode terminals may be connected to each other ateither the proximal or distal ends of the probe to form a single wirethat couples to a power source.

In one configuration, each individual electrode terminal in theelectrode array is electrically insulated from all other electrodeterminals in the array within said probe and is connected to a powersource which is isolated from each of the other electrode terminals inthe array or to circuitry which limits or interrupts current flow to theelectrode terminal when low resistivity material (e.g., blood,electrically conductive saline irrigant or electrically conductive gel)causes a lower impedance path between the return electrode and theindividual electrode terminal. The isolated power sources for eachindividual electrode terminal may be separate power supply circuitshaving internal impedance characteristics which limit power to theassociated electrode terminal when a low impedance return path isencountered. By way of example, the isolated power source may be a userselectable constant current source. In this embodiment, lower impedancepaths will automatically result in lower resistive heating levels sincethe heating is proportional to the square of the operating current timesthe impedance. Alternatively, a single power source may be connected toeach of the electrode terminals through independently actuatableswitches, or by independent current limiting elements, such asinductors, capacitors, resistors and/or combinations thereof. Thecurrent limiting elements may be provided in the probe, connectors,cable, controller or along the conductive path from the controller tothe distal tip of the probe. Alternatively, the resistance and/orcapacitance may occur on the surface of the active electrode terminal(s)due to oxide layers which form selected electrode terminals (e.g.,titanium or a resistive coating on the surface of metal, such asplatinum).

The tip region of the probe may comprise many independent electrodeterminals designed to deliver electrical energy in the vicinity of thetip. The selective application of electrical energy to the conductivefluid is achieved by connecting each individual electrode terminal andthe return electrode to a power source having independently controlledor current limited channels. The return electrode(s) may comprise asingle tubular member of conductive material proximal to the electrodearray at the tip which also serves as a conduit for the supply of theelectrically conducting fluid between the active and return electrodes.Alternatively, the probe may comprise an array of return electrodes atthe distal tip of the probe (together with the active electrodes) tomaintain the electric current at the tip. The application of highfrequency voltage between the return electrode(s) and the electrodearray results in the generation of high electric field intensities atthe distal tips of the electrode terminals with conduction of highfrequency current from each individual electrode terminal to the returnelectrode. The current flow from each individual electrode terminal tothe return electrode(s) is controlled by either active or passive means,or a combination thereof, to deliver electrical energy to thesurrounding conductive fluid while minimizing energy delivery tosurrounding (non-target) tissue.

The application of a high frequency voltage between the returnelectrode(s) and the electrode terminal(s) for appropriate timeintervals effects cutting, removing, ablating, shaping, contracting orotherwise modifying the target tissue. The tissue volume over whichenergy is dissipated (i.e., a high current density exists) may beprecisely controlled, for example, by the use of a multiplicity of smallelectrode terminals whose effective diameters or principal dimensionsrange from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm,and more preferably from about 1 mm to 0.1 mm. Electrode areas for bothcircular and non-circular terminals will have a contact area (perelectrode terminal) below 25 mm², preferably being in the range from0.0001 mm² to 1 mm², and more preferably from 0.005 mm² to 0.5 mm². Thecircumscribed area of the electrode array is in the range from 0.25 mm²to 75 mm², preferably from 0.5 mm² to 40 mm², and will usually includeat least two isolated electrode terminals, preferably at least fiveelectrode terminals, often greater than 10 electrode terminals and even50 or more electrode terminals, disposed over the distal contactsurfaces on the shaft. The use of small diameter electrode terminalsincreases the electric field intensity and reduces the extent or depthof tissue heating as a consequence of the divergence of current fluxlines which emanate from the exposed surface of each electrode terminal.

The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. Activeelectrode surfaces can have areas in the range from 0.25 mm² to 75 mm²,usually being from about 0.5 mm² to 40 mm². The geometries can beplanar, concave, convex, hemispherical, conical, linear “in-line” arrayor virtually any other regular or irregular shape. Most commonly, theactive electrode(s) or electrode terminal(s) will be formed at thedistal tip of the electrosurgical probe shaft, frequently being planar,disk-shaped, or hemispherical surfaces for use in reshaping proceduresor being linear arrays for use in cutting. Alternatively oradditionally, the active electrode(s) may be formed on lateral surfacesof the electrosurgical probe shaft (e.g., in the manner of a spatula),facilitating access to certain body structures in endoscopic procedures.

In the representative embodiments, the electrode terminals comprisesubstantially rigid wires protruding outward from the tissue treatmentsurface of the electrode support member. Usually, the wires will extendabout 0.1 to 4.0 mm, preferably about 0.2 to 1 mm, from the distalsurface of the support member. In the exemplary embodiments, theelectrosurgical probe includes between about two to fifty electricallyisolated electrode terminals, and preferably between about three totwenty electrode terminals.

The electrically conducting fluid should have a threshold conductivityto provide a suitable conductive path between the return electrode(s)and the electrode terminal(s). The electrical conductivity of the fluid(in units of milliSiemans per centimeter or mS/cm) will usually begreater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm.

In some embodiments, the electrode support and the fluid outlet may berecessed from an outer surface of the probe or handpiece to confine theelectrically conductive fluid to the region immediately surrounding theelectrode support. In addition, the shaft may be shaped so as to form acavity around the electrode support and the fluid outlet. This helps toassure that the electrically conductive fluid will remain in contactwith the electrode terminal(s) and the return electrode(s) to maintainthe conductive path therebetween. In addition, this will help tomaintain a vapor or plasma layer between the electrode terminal(s) andthe tissue at the treatment site throughout the procedure, which reducesthe thermal damage that might otherwise occur if the vapor layer wereextinguished due to a lack of conductive fluid. Provision of theelectrically conductive fluid around the target site also helps tomaintain the tissue temperature at desired levels.

The voltage applied between the return electrode(s) and the electrodearray will be at high or radio frequency, typically between about 5 kHzand 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferablybeing between about 50 kHz and 500 kHz, more preferably less than 350kHz, and most preferably between about 100 kHz and 200 kHz. The RMS(root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the electrode terminal size, theoperating frequency and the operation mode of the particular procedureor desired effect on the tissue (i.e., contraction, coagulation orablation). Typically, the peak-to-peak voltage will be in the range of10 to 2000 volts, preferably in the range of 20 to 1200 volts and morepreferably in the range of about 40 to 800 volts (again, depending onthe electrode size, the operating frequency and the operation mode).

As discussed above, the voltage is usually delivered in a series ofvoltage pulses or alternating current of time varying voltage amplitudewith a sufficiently high frequency (e.g., on the order of 5 kHz to 20MHz) such that the voltage is effectively applied continuously (ascompared with e.g., lasers claiming small depths of necrosis, which aregenerally pulsed about 10 to 20 Hz). In addition, the duty cycle (i.e.,cumulative time in any one-second interval that energy is applied) is onthe order of about 50% for the present invention, as compared withpulsed lasers which typically have a duty cycle of about 0.0001%.

The preferred power source of the present invention delivers a highfrequency current selectable to generate average power levels rangingfrom several milliwatts to tens of watts per electrode, depending on thevolume of target tissue being heated, and/or the maximum allowedtemperature selected for the probe tip. The power source allows the userto select the voltage level according to the specific requirements of aparticular FESS procedure, arthroscopic surgery, dermatologicalprocedure, ophthalmic procedures, open surgery or other endoscopicsurgery procedure. A description of a suitable power source can be foundin “SYSTEMS AND METHODS FOR ELECTROSURGICAL TISSUE AND FLUIDCOAGULATION”, filed on Oct. 23, 1997, the complete disclosure of whichhas been incorporated herein by reference.

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In a presently preferred embodiment of thepresent invention, current limiting inductors are placed in series witheach independent electrode terminal, where the inductance of theinductor is in the range of 10 uH to 50,000 uH, depending on theelectrical properties of the target tissue, the desired tissue heatingrate and the operating frequency. Alternatively, capacitor-inductor (LC)circuit structures may be employed, as described previously inco-pending PCT application No. PCT/US94/05168, the complete disclosureof which is incorporated herein by reference. Additionally, currentlimiting resistors may be selected. Preferably, these resistors willhave a large positive temperature coefficient of resistance so that, asthe current level begins to rise for any individual electrode terminalin contact with a low resistance medium (e.g., saline irrigant orconductive gel), the resistance of the current limiting resistorincreases significantly, thereby minimizing the power delivery from saidelectrode terminal into the low resistance medium (e.g., saline irrigantor conductive gel).

It should be clearly understood that the invention is not limited toelectrically isolated electrode terminals, or even to a plurality ofelectrode terminals. For example, the array of active electrodeterminals may be connected to a single lead that extends through theprobe shaft to a power source of high frequency current. Alternatively,the probe may incorporate a single electrode that extends directlythrough the probe shaft or is connected to a single lead that extends tothe power source. The active electrode may have a ball shape (e.g., fortissue vaporization and desiccation), a twizzle shape (for vaporizationand needle-like cutting), a spring shape (for rapid tissue debulking anddesiccation), a twisted metal shape, an annular or solid tube shape orthe like. Alternatively, the electrode may comprise a plurality offilaments, a rigid or flexible brush electrode (for debulking a tumor,such as a fibroid, bladder tumor or a prostate adenoma), a side-effectbrush electrode on a lateral surface of the shaft, a coiled electrode orthe like. In one embodiment, the probe comprises a single activeelectrode terminal that extends from an insulating member, e.g.,ceramic, at the distal end of the probe. The insulating member ispreferably a tubular structure that separates the active electrodeterminal from a tubular or annular return electrode positioned proximalto the insulating member and the active electrode.

Referring now to FIG. 1, an exemplary electrosurgical system 5 forresection, ablation, coagulation and/or contraction of tissue will nowbe described in detail. As shown, electrosurgical system 5 generallyincludes an electrosurgical probe 20 connected to a power supply 10 forproviding high frequency voltage to one or more electrode terminals anda loop electrode (not shown in FIG. 1) on probe 20. Probe 20 includes aconnector housing 44 at its proximal end, which can be removablyconnected to a probe receptacle 32 of a probe cable 22. The proximalportion of cable 22 has a connector 34 to couple probe 20 to powersupply 10. Power supply 10 has an operator controllable voltage leveladjustment 38 to change the applied voltage level, which is observableat a voltage level display 40. Power supply 10 also includes one or morefoot pedals 24 and a cable 26 which is removably coupled to a receptacle30 with a cable connector 28. The foot pedal 24 may also include asecond pedal (not shown) for remotely adjusting the energy level appliedto electrode terminals 104, and a third pedal (also not shown) forswitching between an ablation mode and a coagulation mode. The specificdesign of a power supply which may be used with the electrosurgicalprobe of the present invention is described in Provisional patentapplication entitled “SYSTEMS AND METHODS FOR ELECTROSURGICAL TISSUE ANDFLUID COAGULATION” the full disclosure of which has previously beenincorporated herein by reference.

FIGS. 2-5 illustrate an exemplary electrosurgical probe 20 constructedaccording to the principles of the present invention. As shown in FIG.2, probe 20 generally includes an elongated shaft 100 which may beflexible or rigid, a handle 204 coupled to the proximal end of shaft 100and an electrode support member 102 coupled to the distal end of shaft100. Shaft 100 preferably comprises an electrically conducting material,usually metal, which is selected from the group consisting of tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, and nickel or its alloys. Shaft 100 includesan electrically insulating jacket 108, which is typically formed as oneor more electrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted heatingand necrosis of the structure at the point of contact causing necrosis.

Handle 204 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. As shown in FIG. 3,handle 204 defines an inner cavity 208 that houses the electricalconnections 250 (discussed below), and provides a suitable interface forconnection to an electrical connecting cable 22 (see FIG. 1). As shownin FIG. 5B, the probe will also include a coding resistor 400 having avalue selected to program different output ranges and modes of operationfor the power supply. This allows a single power supply to be used witha variety of different probes in different applications (e.g.,dermatology, cardiac surgery, neurosurgery, arthroscopy, etc). Electrodesupport member 102 extends from the distal end of shaft 100 (usuallyabout 1 to 20 mm), and provides support for a loop electrode 103 and aplurality of electrically isolated electrode terminals 104 (see FIG. 4).

As shown in FIG. 3, the distal portion of shaft 100 is preferably bentto improve access to the operative site of the tissue being treated(e.g., contracted). Electrode support member 102 has a substantiallyplanar tissue treatment surface 212 (see FIG. 4) that is usually at anangle of about 10 to 90 degrees relative to the longitudinal axis ofshaft 100, preferably about 10 to 30 degrees and more preferably about15-18 degrees. In addition, the distal end of the shaft may have abevel, as described in commonly-assigned patent application Ser. No.562,332 filed Nov. 22, 1995. In alternative embodiments, the distalportion of shaft 100 comprises a flexible material which can bedeflected relative to the longitudinal axis of the shaft. Suchdeflection may be selectively induced by mechanical tension of a pullwire, for example, or by a shape memory wire that expands or contractsby externally applied temperature changes. A more complete descriptionof this embodiment can be found in PCT International Application, U.S.National Phase Ser. No. PCT/US94/05168.

The bend in the distal portion of shaft 100 is particularly advantageousin arthroscopic treatment of joint tissue as it allows the surgeon toreach the target tissue within the joint as the shaft 100 extendsthrough a cannula or portal. Of course, it will be recognized that theshaft may have different angles depending on the procedure. For example,a shaft having a 90° bend angle may be particularly useful for accessingtissue located in the back portion of a joint compartment and a shafthaving a 10° to 30° bend angle may be useful for accessing tissue nearor in the front portion of the joint compartment.

As shown in FIG. 4, loop electrode 103 has first and second endsextending from the electrode support member 103. The first and secondends are coupled to, or integral with, a pair of connectors 300, 302,e.g., wires, that extend through the shaft of the probe to its proximalend for coupling to the high frequency power supply. The loop electrodeusually extends about 0.5 to about 10 mm from the distal end of supportmember, preferably about 1 to 2 mm. In the representative embodiment,the loop electrode has a solid construction with a substantially uniformcross-sectional area, e.g., circular, square, etc. Of course, it will berecognized that the ablation electrode may have a wide variety ofcross-sectional shapes, such as annular, square, rectangular, L-shaped,V-shaped, D-shaped, C-shaped, star-shaped and crossed-shaped, asdescribed in commonly-assigned co-pending application Ser. No.08/687,792. In addition, it should be noted that loop electrode 103 mayhave a geometry other than that shown in FIGS. 2-5, such as asemi-circular loop, a V-shaped loop, a straight wire electrode extendingbetween two support members, and the like. Also, loop electrode may bepositioned on a lateral surface of the shaft, or it may extend at atransverse angle from the distal end of the shaft, depending on theparticular surgical procedure.

Loop electrode 103 usually extends further away from the support memberthan the electrode terminals 104 to facilitate resection and ablation oftissue. As discussed below, loop electrode 103 is especially configuredfor resecting fragments or pieces of tissue, while the electrodeterminals ablate or cause molecular dissociation or disintegration ofthe removed pieces from the fluid environment. In the presentlypreferred embodiment, the probe will include 3 to 7 electrode terminalspositioned on either side of the loop electrode. The probe may furtherinclude a suction lumen (not shown) for drawing the pieces of tissuetoward the electrode terminals after they have been removed from thetarget site by the loop electrode 103.

Referring to FIG. 4, the electrically isolated electrode terminals 104are preferably spaced apart over tissue treatment surface 212 ofelectrode support member 102. The tissue treatment surface andindividual electrode terminals 104 will usually have dimensions withinthe ranges set forth above. In the representative embodiment, the tissuetreatment surface 212 has an oval cross-sectional shape with a length Lin the range of 1 mm to 20 mm and a width W in the range from 0.3 mm to7 mm. The oval cross-sectional shape accommodates the bend in the distalportion of shaft 202. The electrode terminals 104 preferably extendslightly outward from surface 212, typically by a distance from 0.2 mmto 2. However, it will be understood that terminals 104 may be flushwith this surface, or even recessed, if desired. In one embodiment ofthe invention, the electrode terminals are axially adjustable relativeto the tissue treatment surface so that the surgeon can adjust thedistance between the surface and the electrode terminals.

In the embodiment shown in FIGS. 2-5, probe 20 includes a returnelectrode 112 for completing the current path between electrodeterminals 104, loop electrode 103 and a high frequency power supply 10(see FIG. 1). As shown, return electrode 112 preferably comprises anannular exposed region of shaft 102 slightly proximal to tissuetreatment surface 212 of electrode support member 102, typically about0.5 to 10 mm and more preferably about 1 to 10 mm. Return electrode 112is coupled to a connector 258 that extends to the proximal end of probe10, where it is suitably connected to power supply 10 (FIG. 1).

As shown in FIG. 2, return electrode 112 is not directly connected toelectrode terminals 104 and loop electrode 103. To complete this currentpath, electrically conducting fluid (e.g., isotonic saline) is caused toflow therebetween. In the representative embodiment, the electricallyconducting fluid is delivered from a fluid delivery element (not shown)that is separate from probe 20. In arthroscopic surgery, for example,the body cavity will be flooded with isotonic saline and the probe 20will be introduced into this flooded cavity. Electrically conductingfluid will be continually resupplied to maintain the conduction pathbetween return electrode 112 and electrode terminals 104 and loopelectrode 103.

In alternative embodiments, the fluid path may be formed in probe 20 by,for example, an inner lumen or an annular gap (not shown) between thereturn electrode and a tubular support member within shaft 100. Thisannular gap may be formed near the perimeter of the shaft 100 such thatthe electrically conducting fluid tends to flow radially inward towardsthe target site, or it may be formed towards the center of shaft 100 sothat the fluid flows radially outward. In both of these embodiments, afluid source (e.g., a bag of fluid elevated above the surgical site orhaving a pumping device), is coupled to probe 20 via a fluid supply tube(not shown) that may or may not have a controllable valve. A morecomplete description of an electrosurgical probe incorporating one ormore fluid lumen(s) can be found in commonly assigned, co-pendingapplication Ser. No. 08/485,219, filed on Jun. 7, 1995, the completedisclosure of which has previously been incorporated herein byreference.

In addition, the probe 20 may include an aspiration lumen (not shown)for aspirating excess conductive fluid, other fluids, such as blood,and/or tissue fragments from the target site. The probe may also includeone or more aspiration electrode(s), such as those described below inreference to FIGS. 8-12, for ablating the aspirated tissue fragments.Alternatively, the aspiration electrode(s) may comprise the activeelectrode terminals described above. For example, the probe may have anaspiration lumen with a distal opening positioned adjacent one or moreof the active electrode terminals at the distal end of the probe. Astissue fragments are drawn into the aspiration lumen, the activeelectrode terminals are energized to ablate at least a portion of thesefragments to inhibit clogging of the lumen.

Referring now to FIG. 6, a surgical kit 300 for resecting and/orablating tissue within a joint according to the invention will now bedescribed. As shown, surgical kit 300 includes a package 302 for housinga surgical instrument 304, and an instructions for use 306 of instrument304. Package 302 may comprise any suitable package, such as a box,carton, wrapping, etc. In the exemplary embodiment, kit 300 furtherincludes a sterile wrapping 320 for packaging and storing instrument304. Instrument 304 includes a shaft 310 having at least one loopelectrode 311 and at least one electrode terminal 312 at its distal end,and at least one connector (not shown) extending from loop electrode 311and electrode terminal 312 to the proximal end of shaft 310. Theinstrument 304 is generally disposable after a single procedure.Instrument 304 may or may not include a return electrode 316.

The instructions for use 306 generally includes the steps of adjusting avoltage level of a high frequency power supply (not shown) to effectresection and/or ablation of tissue at the target site, connecting thesurgical instrument 304 to the high frequency power supply, positioningthe loop electrode 311 and the electrode terminal 312 withinelectrically conductive fluid at or near the tissue at the target site,and activating the power supply. The voltage level is usually about 40to 400 volts rms for operating frequencies of about 100 to 200 kHz. Inthe preferred embodiment, the positioning step includes introducing atleast a distal portion of the instrument 304 through a portal into ajoint.

The present invention is particularly useful for lateral releaseprocedures, or for resecting and ablating a bucket-handle tear of themedial meniscus. In the latter technique, the probe is introducedthrough a medial port and the volume which surrounds the working end ofthe probe is filled with an electrically conductive fluid which may, byway of example, be isotonic saline or other biocompatible, electricallyconductive irrigant solution. When a voltage is applied between the loopelectrode and the return electrode, electrical current flows from theloop electrode, through the irrigant solution to the return electrode.The anterior horn is excised by pressing the exposed portion of the loopelectrode into the tear and removing one or more tissue fragments. Thedisplaced fragments are then ablated with the electrode terminals asdescribed above.

Through a central patellar splitting approach, the probe is then placedwithin the joint through the intercondylar notch, and the attachedposterior horn insertion is resected by pressing the loop electrode intothe attached posterior fragment. The fragment is then removed with theelectrode terminals and the remnant is checked for stability.

Referring now to FIG. 7, an exemplary electrosurgical system 411 fortreatment of tissue in ‘dry fields’ will now be described in detail. Ofcourse, system 411 may also be used in ‘wet field’, i.e., the targetsite is immersed in electrically conductive fluid. However, this systemis particularly useful in ‘dry fields’ where the fluid is preferablydelivered through electrosurgical probe to the target site. As shown,electrosurgical system 411 generally comprises an electrosurgicalhandpiece or probe 410 connected to a power supply 428 for providinghigh frequency voltage to a target site and a fluid source 421 forsupplying electrically conducting fluid 450 to probe 410. In addition,electrosurgical system 411 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site, particularly insinus procedures or procedures in the ear or the back of the mouth. Theendoscope may be integral with probe 410, or it may be part of aseparate instrument. The system 411 may also include a vacuum source(not shown) for coupling to a suction lumen or tube 505 (see FIG. 2) inthe probe 410 for aspirating the target site.

As shown, probe 410 generally includes a proximal handle 419 and anelongate shaft 418 having an array 412 of electrode terminals 458 at itsdistal end. A connecting cable 434 has a connector 426 for electricallycoupling the electrode terminals 458 to power supply 428. The electrodeterminals 458 are electrically isolated from each other and each of theterminals 458 is connected to an active or passive control networkwithin power supply 428 by means of a plurality of individuallyinsulated conductors (not shown). A fluid supply tube 415 is connectedto a fluid tube 414 of probe 410 for supplying electrically conductingfluid 450 to the target site.

Similar to the above embodiment, power supply 428 has an operatorcontrollable voltage level adjustment 430 to change the applied voltagelevel, which is observable at a voltage level display 432. Power supply428 also includes first, second and third foot pedals 437, 438, 439 anda cable 436 which is removably coupled to power supply 428. The footpedals 37, 38, 39 allow the surgeon to remotely adjust the energy levelapplied to electrode terminals 458. In an exemplary embodiment, firstfoot pedal 437 is used to place the power supply into the “ablation”mode and second foot pedal 438 places power supply 428 into the“coagulation” mode. The third foot pedal 439 allows the user to adjustthe voltage level within the “ablation” mode. In the ablation mode, asufficient voltage is applied to the electrode terminals to establishthe requisite conditions for molecular dissociation of the tissue (i.e.,vaporizing a portion of the electrically conductive fluid, ionizingcharged particles within the vapor layer and accelerating these chargedparticles against the tissue). As discussed above, the requisite voltagelevel for ablation will vary depending on the number, size, shape andspacing of the electrodes, the distance in which the electrodes extendfrom the support member, etc. Once the surgeon places the power supplyin the “ablation” mode, voltage level adjustment 430 or third foot pedal439 may be used to adjust the voltage level to adjust the degree oraggressiveness of the ablation.

Of course, it will be recognized that the voltage and modality of thepower supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient methods ofcontrolling the power supply while manipulating the probe during asurgical procedure.

In the coagulation mode, the power supply 428 applies a low enoughvoltage to the electrode terminals (or the coagulation electrode) toavoid vaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternatively stepping on foot pedals 437, 438, respectively. Thisallows the surgeon to quickly move between coagulation and ablation insitu, without having to remove his/her concentration from the surgicalfield or without having to request an assistant to switch the powersupply. By way of example, as the surgeon is sculpting soft tissue inthe ablation mode, the probe typically will simultaneously seal and/orcoagulation small severed vessels within the tissue. However, largervessels, or vessels with high fluid pressures (e.g., arterial vessels)may not be sealed in the ablation mode. Accordingly, the surgeon cansimply step on foot pedal 38, automatically lowering the voltage levelbelow the threshold level for ablation, and apply sufficient pressureonto the severed vessel for a sufficient period of time to seal and/orcoagulate the vessel. After this is completed, the surgeon may quicklymove back into the ablation mode by stepping on foot pedal 437. Aspecific design of a suitable power supply for use with the presentinvention can be found in provisional patent application entitled“SYSTEMS AND METHODS FOR ELECTROSURGICAL TISSUE AND FLUID COAGULATION”,filed Oct. 23, 1997, previously incorporated herein by reference.

FIGS. 8-10 illustrate an exemplary electrosurgical probe 490 constructedaccording to the principles of the present invention. As shown in FIG.2, probe 490 generally includes an elongated shaft 500 which may beflexible or rigid, a handle 604 coupled to the proximal end of shaft 500and an electrode support member 502 coupled to the distal end of shaft500. Shaft 500 preferably includes a bend 501 that allows the distalsection of shaft 500 to be offset from the proximal section and handle604. This offset facilitates procedures that require an endoscope, suchas FESS, because the endoscope can, for example, be introduced throughthe same nasal passage as the shaft 500 without interference betweenhandle 604 and the eyepiece of the endoscope (see FIG. 16). Shaft 500preferably comprises a plastic material that is easily molded into theshape shown in FIG. 1.

In an alternative embodiment (not shown), shaft 500 comprises anelectrically conducting material, usually metal, which is selected fromthe group comprising tungsten, stainless steel alloys, platinum or itsalloys, titanium or its alloys, molybdenum or its alloys, and nickel orits alloys. In this embodiment, shaft 500 includes an electricallyinsulating jacket 508, which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted heatingand necrosis of the structure at the point of contact causing necrosis.

Handle 604 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. Handle 604 defines aninner cavity (not shown) that houses the electrical connections 650(FIG. 10), and provides a suitable interface for connection to anelectrical connecting cable 22 (see FIG. 7). Electrode support member502 extends from the distal end of shaft 500 (usually about 1 to 20 mm),and provides support for a plurality of electrically isolated electrodeterminals 504 (see FIG. 9). As shown in FIG. 8, a fluid tube 633 extendsthrough an opening in handle 604, and includes a connector 635 forconnection to a fluid supply source, for supplying electricallyconductive fluid to the target site. Depending on the configuration ofthe distal surface of shaft 500, fluid tube 633 may extend through asingle lumen (not shown) in shaft 500, or it may be coupled to aplurality of lumens (also not shown) that extend through shaft 500 to aplurality of openings at its distal end. In the representativeembodiment, fluid tube 633 extends along the exterior of shaft 500 to apoint just proximal of return electrode 512 (see FIG. 9). In thisembodiment, the fluid is directed through an opening 637 past returnelectrode 512 to the electrode terminals 504. Probe 490 may also includea valve 417 (FIG. 1) or equivalent structure for controlling the flowrate of the electrically conducting fluid to the target site.

As shown in FIG. 8, the distal portion of shaft 500 is preferably bentto improve access to the operative site of the tissue being treated.Electrode support member 502 has a substantially planar tissue treatmentsurface 612 that is usually at an angle of about 10 to 90 degreesrelative to the longitudinal axis of shaft 600, preferably about 30 to60 degrees and more preferably about 45 degrees. In alternativeembodiments, the distal portion of shaft 500 comprises a flexiblematerial which can be deflected relative to the longitudinal axis of theshaft. Such deflection may be selectively induced by mechanical tensionof a pull wire, for example, or by a shape memory wire that expands orcontracts by externally applied temperature changes. A more completedescription of this embodiment can be found in PCT InternationalApplication, U.S. National Phase Ser. No. PCT/US94/05168, filed on May10, 1994, now U.S. Pat. No. 5,697,909, the complete disclosure of whichhas previously been incorporated herein by reference.

The bend in the distal portion of shaft 500 is particularly advantageousin the treatment of sinus tissue as it allows the surgeon to reach thetarget tissue within the nose as the shaft 500 extends through the nasalpassage. Of course, it will be recognized that the shaft may havedifferent angles depending on the procedure. For example, a shaft havinga 90° bend angle may be particularly useful for accessing tissue locatedin the back portion of the mouth and a shaft having a 10° to 30° bendangle may be useful for accessing tissue near or in the front portion ofthe mouth or nose

In the embodiment shown in FIGS. 8-10, probe 490 includes a returnelectrode 512 for completing the current path between electrodeterminals 504 and a high frequency power supply 28 (see FIG. 1). Asshown, return electrode 512 preferably comprises an annular conductiveband coupled to the distal end of shaft 500 slightly proximal to tissuetreatment surface 612 of electrode support member 502, typically about0.5 to 10 mm and more preferably about 1 to 10 mm. Return electrode 512is coupled to a connector 658 that extends to the proximal end of probe410, where it is suitably connected to power supply 410 (FIG. 7).

As shown in FIG. 8, return electrode 512 is not directly connected toelectrode terminals 504. To complete this current path so that electrodeterminals 504 are electrically connected to return electrode 512,electrically conducting fluid (e.g., isotonic saline) is caused to flowtherebetween. In the representative embodiment, the electricallyconducting fluid is delivered through fluid tube 633 to opening 637, asdescribed above. Alternatively, the fluid may be delivered by a fluiddelivery element (not shown) that is separate from probe 490. Inarthroscopic surgery, for example, the body cavity will be flooded withisotonic saline and the probe 490 will be introduced into this floodedcavity. Electrically conducting fluid will be continually resupplied tomaintain the conduction path between return electrode 512 and electrodeterminals 504.

In alternative embodiments, the fluid path may be formed in probe 490by, for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 500. This annulargap may be formed near the perimeter of the shaft 500 such that theelectrically conducting fluid tends to flow radially inward towards thetarget site, or it may be formed towards the center of shaft 500 so thatthe fluid flows radially outward. In both of these embodiments, a fluidsource (e.g., a bag of fluid elevated above the surgical site or havinga pumping device), is coupled to probe 490 via a fluid supply tube (notshown) that may or may not have a controllable valve. A more completedescription of an electrosurgical probe incorporating one or more fluidlumen(s) can be found in parent application Ser. No. 08/485,219, filedon Jun. 7, 1995, the complete disclosure of which has previously beenincorporated herein by reference.

Referring to FIG. 9, the electrically isolated electrode terminals 504are spaced apart over tissue treatment surface 612 of electrode supportmember 502. The tissue treatment surface and individual electrodeterminals 504 will usually have dimensions within the ranges set forthabove. As shown, the probe includes a single, larger opening 609 in thecenter of tissue treatment surface 612, and a plurality of electrodeterminals (e.g., about 3-15) around the perimeter of surface 612 (seeFIG. 9). Alternatively, the probe may include a single, annular, orpartially annular, electrode terminal at the perimeter of the tissuetreatment surface. The central opening 609 is coupled to a suction lumen(not shown) within shaft 500 and a suction tube 611 (FIG. 8) foraspirating tissue, fluids and/or gases from the target site. In thisembodiment, the electrically conductive fluid generally flows radiallyinward past electrode terminals 504 and then back through the opening609. Aspirating the electrically conductive fluid during surgery allowsthe surgeon to see the target site, and it prevents the fluid fromflowing into the patient's body, e.g., through the sinus passages, downthe patient's throat or into the ear canal.

As shown, one or more of the electrode terminals 504 comprise loopelectrodes 540 that extend across distal opening 609 of the suctionlumen within shaft 500. In the representative embodiment, two of theelectrode terminals 504 comprise loop electrodes 540 that cross over thedistal opening 609. Of course, it will be recognized that a variety ofdifferent configurations are possible, such as a single loop electrode,or multiple loop electrodes having different configurations than shown.In addition, the electrodes may have shapes other than loops, such asthe coiled configurations shown in FIGS. 11 and 12. Alternatively, theelectrodes may be formed within suction lumen proximal to the distalopening 609, as shown in FIG. 13. The main function of loop electrodes540 is to ablate portions of tissue that are drawn into the suctionlumen to prevent clogging of the lumen.

Loop electrodes 540 are electrically isolated from the other electrodeterminals 504, which can be referred to hereinafter as the ablationelectrodes 504. Loop electrodes 540 may or may not be electricallyisolated from each other. Loop electrodes 540 will usually extend onlyabout 0.05 to 4 mm, preferably about 0.1 to 1 mm from the tissuetreatment surface of electrode support member 504.

Of course, it will be recognized that the distal tip of probe may have avariety of different configurations. For example, the probe may includea plurality of openings 609 around the outer perimeter of tissuetreatment surface 612. In this embodiment, the electrode terminals 504extend from the center of tissue treatment surface 612 radially inwardfrom openings 609. The openings are suitably coupled to fluid tube 633for delivering electrically conductive fluid to the target site, and asuction tube 611 for aspirating the fluid after it has completed theconductive path between the return electrode 512 and the electrodeterminals 504. In this embodiment, the ablation electrode terminals 504are close enough to openings 609 to ablate most of the large tissuefragments that are drawn into these openings.

FIG. 10 illustrates the electrical connections 650 within handle 604 forcoupling electrode terminals 504 and return electrode 512 to the powersupply 428. As shown, a plurality of wires 652 extend through shaft 500to couple terminals 504 to a plurality of pins 654, which are pluggedinto a connector block 656 for coupling to a connecting cable 422 (FIG.1). Similarly, return electrode 512 is coupled to connector block 656via a wire 658 and a plug 660.

In use, the distal portion of probe 490 is introduced to the target site(either endoscopically, through an open procedure, or directly onto thepatient's skin) and electrode terminals 504 are positioned adjacenttissue. Electrically conductive fluid is delivered through tube 633 andopening 637 to the tissue. The fluid flows past the return electrode 512to the electrode terminals 504 at the distal end of the shaft. The rateof fluid flow is controlled with valve 417 (FIG. 1) such that the zonebetween the tissue and electrode support 502 is constantly immersed inthe fluid. The power supply 428 is then turned on and adjusted such thata high frequency voltage difference is applied between electrodeterminals 504 and return electrode 512. The electrically conductivefluid provides the conduction path (see current flux lines) betweenelectrode terminals 504 and the return electrode 512.

In the representative embodiment, the high frequency voltage issufficient to convert the electrically conductive fluid (not shown)between the target tissue and electrode terminals 504 into an ionizedvapor layer or plasma (not shown). As a result of the applied voltagedifference between electrode terminal(s) 504 and the target tissue(i.e., the voltage gradient across the plasma layer), charged particlesin the plasma (viz., electrons) are accelerated towards the tissue. Atsufficiently high voltage differences, these charged particles gainsufficient energy to cause dissociation of the molecular bonds withintissue structures. This molecular dissociation is accompanied by thevolumetric removal (i.e, ablative sublimation) of tissue and theproduction of low molecular weight gases, such as oxygen, nitrogen,carbon dioxide, hydrogen and methane. The short range of the acceleratedcharged particles within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue.

During the process, the gases will be aspirated through opening 609 andsuction tube 611 to a vacuum source. In addition, excess electricallyconductive fluid, and other fluids (e.g., blood) will be aspirated fromthe target site to facilitate the surgeon's view. Applicant has alsofound that tissue fragments are also aspirated through opening 609 intosuction lumen and tube 611 during the procedure. These tissue fragmentsare ablated or dissociated with loop electrodes 540 with a similarmechanism described above. Namely, as electrically conductive fluid andtissue fragments are aspirated into loop electrodes 540, theseelectrodes are activated so that high frequency voltage is applied toloop electrodes 540 and return electrode 512 (of course, the probe mayinclude a different, separate return electrode for this purpose). Thevoltage is sufficient to vaporize the fluid, and create a plasma layerbetween loop electrodes 540 and the tissue fragments so that portions ofthe tissue fragments are ablated or removed. This reduces the volume ofthe tissue fragments as they pass through suction lumen to minimizeclogging of the lumen.

In addition, the present invention is particularly useful for removingelastic tissue, such as the synovial tissue found in joints. Inarthroscopic procedures, this elastic synovial tissue tends to move awayfrom instruments within the conductive fluid, making it difficult forconventional instruments to remove this tissue. With the presentinvention, the probe is moved adjacent the target synovial tissue, andthe vacuum source is activated to draw the synovial tissue towards thedistal end of the probe. The aspiration and/or active electrodeterminals are then energized to ablate this tissue. This allows thesurgeon to quickly and precisely ablate elastic tissue with minimalthermal damage to the treatment site.

In one embodiment, loop electrodes 540 are electrically isolated fromthe other electrode terminals 504, and they must be separately activatedat the power supply 428. In other embodiments, loop electrodes 540 willbe activated at the same time that electrode terminals 504 areactivated. In this case, applicant has found that the plasma layertypically forms when tissue is drawn adjacent to loop electrodes 540.

Referring now to FIGS. 11 and 12, alternative embodiments for aspirationelectrodes will now be described. As shown in FIG. 11, the aspirationelectrodes may comprise a pair of coiled electrodes 550 that extendacross distal opening 609 of the suction lumen. The larger surface areaof the coiled electrodes 550 usually increases the effectiveness of theelectrodes 550 on tissue fragments passing through opening 609. In FIG.12, the aspiration electrode comprises a single coiled electrode 552passing across the distal opening 609 of suction lumen. This singleelectrode 552 may be sufficient to inhibit clogging of the suctionlumen. Alternatively, the aspiration electrodes may be positioned withinthe suction lumen proximal to the distal opening 609. Preferably, theseelectrodes are close to opening 609 so that tissue does not clog theopening 609 before it reaches electrodes 554. In this embodiment, aseparate return electrode 556 may be provided within the suction lumento confine the electric currents therein.

Referring to FIG. 13, another embodiment of the present inventionincorporates an aspiration electrode 560 within the aspiration lumen 562of the probe. As shown, the electrode 560 is positioned just proximal ofdistal opening 609 so that the tissue fragments are ablated as theyenter lumen 562. In the representation embodiment, the aspirationelectrode 560 comprises a loop electrode that stretches across theaspiration lumen 562. However, it will be recognized that many otherconfigurations are possible. In this embodiment, the return electrode564 is located outside of the probe as in the previously embodiments.Alternatively, the return electrode(s) may be located within theaspiration lumen 562 with the aspiration electrode 560. For example, theinner insulating coating 563 may be exposed at portions within the lumen562 to provide a conductive path between this exposed portion of returnelectrode 564 and the aspiration electrode 560. The latter embodimenthas the advantage of confining the electric currents to within theaspiration lumen. In addition, in dry fields in which the conductivefluid is delivered to the target site, it is usually easier to maintaina conductive fluid path between the active and return electrodes in thelatter embodiment because the conductive fluid is aspirated through theaspiration lumen 562 along with the tissue fragments.

FIGS. 14-17 illustrate a method for treating nasal or sinus blockages,e.g., chronic sinusitis, according to the present invention. In theseprocedures, the polyps, turbinates or other sinus tissue may be ablatedor reduced (e.g., by tissue contraction) to clear the blockage and/orenlarge the sinus cavity to reestablish normal sinus function. Forexample, in chronic rhinitis, which is a collective term for chronicirritation or inflammation of the nasal mucosa with hypertrophy of thenasal mucosa, the inferior turbinate may be reduced by ablation orcontraction. Alternatively, a turbinectomy or mucotomy may be performedby removing a strip of tissue from the lower edge of the inferiorturbinate to reduce the volume of the turbinate. For treating nasalpolypi, which comprises benign pedicled or sessile masses of nasal orsinus mucosa caused by inflammation, the nasal polypi may be contractedor shrunk, or ablated by the method of the present invention. Fortreating severe sinusitis, a frontal sinus operation may be performed tointroduce the electrosurgical probe to the site of blockage. The presentinvention may also be used to treat diseases of the septum, e.g.,ablating or resecting portions of the septum for removal, straighteningor reimplantation of the septum.

The present invention is particularly useful in functional endoscopicsinus surgery (FESS) in the treatment of sinus disease. In contrast toprior art microdebriders, the electrosurgical probe of the presentinvention effects hemostasis of severed blood vessels, and allows thesurgeon to precisely remove tissue with minimal or no damage tosurrounding tissue, bone, cartilage or nerves. By way of example and notlimitation, the present invention may be used for the followingprocedures: (1) uncinectomy or medial displacement or removal ofportions of the middle turbinate; (2) maxillary, sphenoid or ethmoidsinusotomies or enlargement of the natural ostium of the maxillary,sphenoid, or ethmoid sinuses, respectively; (3) frontal recessdissections, in which polypoid or granulation tissue are removed; (4)polypectomies, wherein polypoid tissue is removed in the case of severenasal polyposis; (5) concha bullosa resections or the thinning ofpolypoid middle turbinate; (6) septoplasty; and the like.

FIGS. 14-17 schematically illustrate an endoscopic sinus surgery (FESS)procedure according to the present invention. As shown in FIG. 14, anendoscope 700 is first introduced through one of the nasal passages 701to allow the surgeon to view the target site, e.g., the sinus cavities.As shown, the endoscope 700 will usually comprise a thin metal tube 702with a lens (not shown) at the distal end 704, and an eyepiece 706 atthe proximal end 708. As shown in FIG. 8, the probe shaft 500 has a bend501 to facilitate use of both the endoscope and the probe 490 in thesame nasal passage (i.e., the handles of the two instruments do notinterfere with each other in this embodiment). Alternatively, theendoscope may be introduced transorally through the inferior soft palateto view the nasopharynx. Suitable nasal endoscopes for use with thepresent invention are described in U.S. Pat. Nos. 4,517,962, 4,844,052,4,881,523 and 5,167,220, the complete disclosures of which areincorporated herein by reference for all purposes.

Alternatively, the endoscope 700 may include a sheath (not shown) havingan inner lumen for receiving the electrosurgical probe shaft 500. Inthis embodiment, the shaft 500 will extend through the inner lumen to adistal opening in the endoscope. The shaft will include suitableproximal controls for manipulation of its distal end during the surgicalprocedure.

As shown in FIG. 15, the distal end of probe 490 is introduced throughnasal passage 701 into the nasal cavity 703 (endoscope 700 is not shownin FIG. 12). Depending on the location of the blockage, the electrodeterminals 504 will be positioned adjacent the blockage in the nasalcavity 703, or in one of the paranasal sinuses 705, 707. Note that onlythe frontal sinus 705 and the sphenoidal sinus 707 are shown in FIG. 12,but the procedure is also applicable to the ethmoidal and maxillarysinuses. Once the surgeon has reached the point of major blockage,electrically conductive fluid is delivered through tube 633 and opening637 to the tissue (see FIG. 8). The fluid flows past the returnelectrode 512 to the electrode terminals 504 at the distal end of theshaft. The rate of fluid flow is controlled with valve 417 (FIG. 8) suchthat the zone between the tissue and electrode support 502 is constantlyimmersed in the fluid. The power supply 428 is then turned on andadjusted such that a high frequency voltage difference is appliedbetween electrode terminals 504 and return electrode 512. Theelectrically conductive fluid provides the conduction path (see currentflux lines) between electrode terminals 504 and the return electrode512.

FIGS. 16A and 16B illustrate the removal of sinus tissue in more detailAs shown, the high frequency voltage is sufficient to convert theelectrically conductive fluid (not shown) between the target tissue 702and electrode terminal(s) 504 into an ionized vapor layer 712 or plasma.As a result of the applied voltage difference between electrodeterminal(s) 504 (or electrode terminal 458) and the target tissue 702(i.e., the voltage gradient across the plasma layer 712), chargedparticles 715 in the plasma (viz., electrons) are accelerated towardsthe tissue. At sufficiently high voltage differences, these chargedparticles 715 gain sufficient energy to cause dissociation of themolecular bonds within tissue structures. This molecular dissociation isaccompanied by the volumetric removal (i.e, ablative sublimation) oftissue and the production of low molecular weight gases 714, such asoxygen, nitrogen, carbon dioxide, hydrogen and methane. The short rangeof the accelerated charged particles 715 within the tissue confines themolecular dissociation process to the surface layer to minimize damageand necrosis to the underlying tissue 720.

During the process, the gases 714 will be aspirated through opening 609and suction tube 611 to a vacuum source. In addition, excesselectrically conductive fluid, and other fluids (e.g., blood) will beaspirated from the target site 700 to facilitate the surgeon's view.During ablation of the tissue, the residual heat generated by thecurrent flux lines (typically less than 150° C.), will usually besufficient to coagulate any severed blood vessels at the site. If not,the surgeon may switch the power supply 428 into the coagulation mode bylowering the voltage to a level below the threshold for fluidvaporization, as discussed above. This simultaneous hemostasis resultsin less bleeding and facilitates the surgeon's ability to perform theprocedure. Once the blockage has been removed, aeration and drainage arereestablished to allow the sinuses to heal and return to their normalfunction.

Another advantage of the present invention is the ability to preciselyablate layers of sinus tissue without causing necrosis or thermal damageto the underlying and surrounding tissues, nerves (e.g., the opticnerve) or bone. In addition, the voltage can be controlled so that theenergy directed to the target site is insufficient to ablate bone oradipose tissue (which generally has a higher impedance than the targetsinus tissue). In this manner, the surgeon can literally clean thetissue off the bone, without ablating or otherwise effecting significantdamage to the bone.

Methods for treating air passage disorders according to the presentinvention will now be described. In these embodiments, anelectrosurgical probe such as one described above can be used to ablatetargeted masses including, but not limited to, the tongue, tonsils,turbinates, soft palate tissues (e.g., the uvula), hard tissue andmucosal tissue. In one embodiment, selected portions of the tongue 714are removed to treat sleep apnea. In this method, the distal end of anelectrosurgical probe 490 is introduced into the patient's mouth 710, asshown in FIG. 17. An endoscope (not shown), or other type of viewingdevice, may also be introduced, or partially introduced, into the mouth710 to allow the surgeon to view the procedure (the viewing device maybe integral with, or separate from, the electrosurgical probe). Theelectrode terminals 104 are positioned adjacent to or against the backsurface 716 of the tongue 714, and electrically conductive fluid isdelivered to the target site, as described above. The power supply 428is then activated to remove selected portions of the back of the tongue714, as described above, without damaging sensitive structures, such asnerves, and the bottom portion of the tongue 714.

In another embodiment, the electrosurgical probe of the presentinvention can be used to ablate and/or contract soft palate tissue totreat snoring disorders. In particular, the probe is used to ablate orshrink sections of the uvula 720 without causing unwanted tissue damageunder and around the selected sections of tissue. For tissuecontraction, a sufficient voltage difference is applied between theelectrode terminals 504 and the return electrode 512 to elevate theuvula tissue temperature from normal body temperatures (e.g., 37° C.) totemperatures in the range of 45° C. to 90° C., preferably in the rangefrom 60° C. to 70° C. This temperature elevation causes contraction ofthe collagen connective fibers within the uvula tissue.

In addition to the above procedures, the system and method of thepresent invention may be used for treating a variety of disorders in themouth 710, pharynx 730, larynx 735, hypopharynx, trachea 740, esophagus750 and the neck 760. For example, tonsillar hyperplasis or other tonsildisorders may be treated with a tonsillectomy by partially ablating thelymphoepithelial tissue. This procedure is usually carried out underintubation anesthesia with the head extended. An incision is made in theanterior faucial pillar, and the connective tissue layer between thetonsillar parenchyma and the pharyngeal constrictor muscles isdemonstrated. The incision may be made with conventional scalpels, orwith the electrosurgical probe of the present invention. The tonsil isthen freed by ablating through the upper pole to the base of the tongue,preserving the faucial pillars. The probe ablates the tissue, whileproviding simultaneous hemostasis of severed blood vessels in theregion. Similarly, adenoid hyperplasis, or nasal obstruction leading tomouth breathing difficulty, can be treated in an adenoidectomy byseparating (e.g., resecting or ablating) the adenoid from the base ofthe nasopharynx.

Other pharyngeal disorders can be treated according to the presentinvention. For example, hypopharyngeal diverticulum involves smallpouches that form within the esophagus immediately above the esophagealopening. The sac of the pouch may be removed endoscopically according tothe present invention by introducing a rigid esophagoscope, andisolating the sac of the pouch. The cricopharyngeus muscle is thendivided, and the pouch is ablated according to the present invention.Tumors within the mouth and pharynx, such as hemangionmas,lymphangiomas, papillomas, lingual thyroid tumors, or malignant tumors,may also be removed according to the present invention.

Other procedures of the present invention include removal of vocal cordpolyps and lesions and partial or total laryngectomies. In the latterprocedure, the entire larynx is removed from the base of the tongue tothe trachea, if necessary with removal of parts of the tongue, thepharynx, the trachea and the thyroid gland.

Tracheal stenosis may also be treated according to the presentinvention. Acute and chronic stenoses within the wall of the trachea maycause coughing, cyanosis and choking.

The system and method of the present invention may also be useful toefficaciously ablate (i.e., disintegrate) cancer cells and tissuecontaining cancer cells, such as cancer on the surface of the epidermis,eye, colon, bladder, cervix, uterus and the like. The presentinvention's ability to completely disintegrate the target tissue can beadvantageous in this application because simply vaporizing andfragmenting cancerous tissue may lead to spreading of viable cancercells (i.e., seeding) to other portions of the patient's body or to thesurgical team in close proximity to the target tissue. In addition, thecancerous tissue can be removed to a precise depth while minimizingnecrosis of the underlying tissue.

Other modifications and variations can be made to disclose embodimentswithout departing from the subject invention as defined in the followingclaims. For example, it should be noted that the invention is notlimited to an electrode array comprising a plurality of electrodeterminals. The invention could utilize a plurality of return electrodes,e.g., in a bipolar array or the like. In addition, depending on otherconditions, such as the peak-to-peak voltage, electrode diameter, etc.,a single electrode terminal may be sufficient to contract collagentissue, ablate tissue, or the like.

In addition, the active and return electrodes may both be located on adistal tissue treatment surface adjacent to each other. The active andreturn electrodes may be located in active/return electrode pairs, orone or more return electrodes may be located on the distal tip togetherwith a plurality of electrically isolated electrode terminals. Theproximal return electrode may or may not be employed in theseembodiments. For example, if it is desired to maintain the current fluxlines around the distal tip of the probe, the proximal return electrodewill not be desired.

What is claimed is:
 1. An apparatus for applying electrical energy totissue at a target site comprising: an electrosurgical instrument havinga shaft with a proximal end portion, a distal end portion and anaspiration lumen therebetween, the aspiration lumen having a distalopening at or near the distal end portion of the shaft; a high frequencypower supply; a return electrode electrically coupled to the highfrequency power supply; and an aspiration electrode on the shaftcomprising a loop electrode extending across the distal opening of theaspiration lumen; and a connector near the proximal end of the shaftelectrically coupling the aspiration electrode to the high frequencypower supply.
 2. The apparatus of claim 1 wherein the aspirationelectrode comprises two or more loop electrodes.
 3. The apparatus ofclaim 1 further comprising an ablation electrode on the instrument shaftelectrically isolated from the aspiration electrode, wherein the returnelectrode is spaced proximally from the ablation electrode.
 4. Theapparatus of claim 1 further comprising an electrode array ofelectrically isolated ablation electrode terminals on the instrumentshaft, the ablation electrode terminals being electrically isolated fromthe aspiration electrode.
 5. The apparatus of claim 1 further comprisinga fluid delivery element defining a fluid path in electrical contactwith the return electrode and the aspiration electrode to generate acurrent flow path between the return electrode and the aspirationelectrode.
 6. The apparatus of claim 1 wherein the return electrodeforms a portion of the shaft.
 7. The apparatus of claim 1 furtherincluding an insulating member positioned between the return electrodeand the aspiration electrode, the return electrode being sufficientlyspaced from the aspiration electrode to minimize direct contact betweenthe return electrode and a body structure at the target site when theaspiration electrode is positioned in close proximity or in partialcontact with the body structure.
 8. An apparatus for applying electricalenergy to tissue at a target site comprising: an electrosurgicalinstrument having a shaft with a proximal end portion, a distal endportion and an aspiration lumen therebetween, the aspiration lumenhaving a distal opening at or near the distal end portion of the shaft;a high frequency power supply; a return electrode electrically coupledto the high frequency power supply; and an aspiration electrode on theshaft in contact with the aspiration lumen; an ablation electrode on theinstrument shaft electrically isolated from the aspiration electrode,wherein the return electrode is spaced proximally from the ablationelectrode; and a connector near the proximal end of the shaftelectrically coupling the aspiration electrode to the high frequencypower supply.
 9. The apparatus of claim 8 further comprising anelectrode array of electrically isolated ablation electrode terminals onthe instrument shaft, the ablation electrode terminals beingelectrically isolated from the aspiration electrode.
 10. The apparatusof claim 8 further comprising a fluid delivery element defining a fluidpath in electrical contact with the return electrode and the ablationelectrode to generate a current flow path between the return electrodeand the ablation electrode.
 11. The apparatus of claim 8 wherein thereturn electrode forms a portion of the shaft.
 12. The apparatus ofclaim 8 further including an insulating member positioned between thereturn electrode and the ablation electrode, the return electrode beingsufficiently spaced from the ablation electrode to minimize directcontact between the return electrode and a body structure at the targetsite when the ablation electrode is positioned in close proximity or inpartial contact with the body structure.
 13. The apparatus of claim 8wherein the aspiration electrode is positioned adjacent the distalopening of the aspiration lumen.
 14. The apparatus of claim 8 whereinthe aspiration electrode is positioned across the distal opening of theaspiration lumen.
 15. The apparatus of claim 8 wherein the aspirationelectrode is positioned within the aspiration lumen proximal to thedistal opening.
 16. The apparatus of claim 8 wherein the aspirationelectrode comprises a loop electrode extending across the distal openingof the aspiration lumen.
 17. The apparatus of claim 8 wherein theaspiration electrode comprises two or more loop electrodes.
 18. Theapparatus of claim 8 wherein the aspiration electrode comprises one ormore coiled electrodes.